FIG. 15 shows a conventional cleaning robot which comprises a robot body 9 provided with drive wheels 92, a cleaning mechanism 91 mounted on the body and a plurality of ultrasonic sensors 93 provided on the outer sides of the body and directed outward.
When a memory card 95 having recorded thereon dimensional data as to the room to be cleaned is inserted into an inlet 94 of the robot body 9, followed by actuation of a start switch 96, the dimensional data is first read from the memory card 95, and a travel path of the cleaning robot is initially set based on the data. The robot body 9 then starts to travel along the path.
During the travel of the robot body 9, the distances from the robot to side walls or obstacles (hereinafter referred to collectively as the side wall) which are present in the cleaning area are measured by the ultrasonic sensors 93, and an internal map is prepared from the measurements. The travel path of the robot is corrected by ensuring a match between the internal map and the path. Consequently, the robot is able to clean the floor while avoiding a collision with the side wall.
With the conventional cleaning robot, however, the detecting ability of the ultrasonic sensors 93 is governed by the material, configuration or the like of the side wall, so that the distances to the side wall detected are likely to involve errors, which make the internal map inaccurate, possibly permitting the robot to collide with the side wall.
Furthermore, the ultrasonic sensors 93 for measuring distances are low in sensitivity to variations in distance, so that there is a need to set the robot at a large distance from the side wall when the robot travels along the side wall. This entails the problem that an area close to the side wall remains uncleaned.